WASHINGTON — State prison inmates, particularly blacks, are living longer on average than people on the outside, the government said yesterday.

Inmates in state prisons are dying at an average yearly rate of 250 out of every 100,000, according to the latest figures reported to the Justice Department by state prison officials. By comparison, the overall population of people between age 15 and 64 is dying at a rate of 308 a year.

For black inmates, the rate was 57% lower than among the overall black population — 206 versus 484. But white and Hispanic prisoners both had death rates slightly below their counterparts in the overall population.

The Justice Department’s Bureau of Justice Statistics said 12,129 state prisoners died between 2001 through 2004.

Eight percent were murdered or killed themselves, 2% died of alcohol, drugs, or accidental injuries, and 1% of the deaths could not be explained, the report said.

The rest of the deaths — 89% — were due to medical reasons. Of those, two-thirds of inmates died of the medical problem that they had before they were admitted to prison.

Medical problems that were most common among both men and women in state prisons were heart disease, lung and liver cancer, liver diseases, and AIDS-related causes.

But the death rate among men was 72% higher than among women. Nearly one-quarter of the women who died had breast, ovarian, cervical, or uterine cancer.

Four percent of the men who died had prostate or testicular cancer.

More than half the inmates 65 or older who died in state prisons were at least 55 when they were admitted to prison.

State prison officials reported that 94% of their inmates who died from an illness had been evaluated by a medical professional for that illness, and 93% got medication for it.

Eighty-nine percent of these inmates had gotten X-rays, MRI exams, blood tests, and other diagnostic work, state prison officials told the bureau.